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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 60 |
| 5 | 302 |
| 6 | 1812 |
| 7 | 12685 |
| 8 | 101486 |
| 9 | 913377 |
| 10 | 9133773 |
| 11 | 100471510 |
| 12 | 1205658127 |
| 13 | 15673555658 |
| 14 | 219429779214 |
| 15 | 3291446688215 |
| 16 | 52663147011442 |
| 17 | 895273499194524 |
| 18 | 16114922985501439 |
| 19 | 306183536724527356 |
| 20 | 6123670734490547129 |
[2,5,15,60,302,1812,12685,101486,913377,9133773, 100471510,1205658127,15673555658,219429779214, 3291446688215,52663147011442,895273499194524, 16114922985501439,306183536724527356, 6123670734490547129] |